Some vehicles, including passenger cars and trucks, use single-piston hydraulic brake systems for vehicle deceleration. These vehicles may also have a parking brake system that utilizes the same single piston of the service brake for creating clamping force to maintain the vehicle in a stopped or parked position. In these parking brake systems, a motor may generate sufficient torque to move the single piston, and therefore, the brake pads against the brake rotor to create the clamping brake force.
Other vehicle platforms, like full-size trucks, vans, and SUVs, use multi-piston hydraulic brake systems only for vehicle deceleration, and a separate parking brake system for maintaining the vehicle in a parked position.
To improve parking brake performance, while also reducing weight, costs, complexity, assembly time, and packaging space, in some vehicle platforms, it may be desirable to have a parking brake system that utilizes an existing multi-piston brake system of the service brake without requiring a super high output motor to move all of the pistons and the brake pads against the brake rotor to create the clamping force. For example, it may be attractive to have a parking brake system for a heavy-duty vehicle platform with a multi-piston brake system that can use a motor from a light-duty vehicle platform to sufficiently move the pistons and brake pads against a brake rotor to create a sufficient clamping force. For example, rather than using a large motor, multiple motors, or motors from a heavy-duty application, all of which can be costly and heavy, it may also be desirable to use a motor from a light-duty vehicle platform to move multiple pistons and brake pads against a brake rotor to create a sufficient clamping force and also prevent the clamping force or motor from releasing or back driving after the clamping force has been created.